1. Field of the Invention
The present invention relates to a zoom lens achieving a wide angle of view represented by a half angle of view of about 40 degrees at its wide-angle end; and, in particular, to a wide-angle zoom lens suitable for a TV camera.
1. Description of the Prior Art
In general, lenses capable of taking pictures with a wide angle of view have been required for video cameras and professional TV cameras. In addition, as imaging devices for video cameras are reducing their size, there has recently been a demand for wide-angle zoom lenses having a small-size lens system as a whole, a high aperture ratio, a high variable power ratio, and a high performance.
In a wide-angle zoom lens, however, the first group tends to have a larger lens diameter, and a larger number of lenses are necessary due to its severe requirement for aberration correction, thus making it difficult to reduce the size and weight of the lens.
Proposed in view of such a demand, for example, are lens systems disclosed in Japanese Unexamined Patent Publication Nos. 5-72475, 6-242378, and 9-33812.
Though the lens system disclosed in Japanese Unexamined Patent Publication No. 5-72475 attempts to reduce its size and weight by using a first lens group having a relatively small number of lenses, i.e., 5, its half angle of view is about 35 degrees, thus leaving a demand for lenses with a wider angle of view.
On the other hand, though the lens system disclosed in Japanese Unexamined Patent Publication No. 6-242378 or 9-33812 achieves a wide angle of view, a first lens group having a large lens diameter is composed of 9 or 10 sheets, thus being disadvantageous from the viewpoint of reducing the size and weight.